The EconomistSeptember 21st 2019 Europe 45“T
his onehas seen Napoleon,” says Massimo Arsieni. “It has
seen the world wars. It has seen everything. And soon it will
be dead.” He throws his arms around the fat, gnarled trunk of the
olive tree. He means to emphasise its age, but could be clasping a
dying relative. Mr Arsieni’s family has owned these groves outside
the village of Cellino San Marco since 1800. Though harvest season
is drawing near in Puglia, in the heel of the Italian boot, the tree’s
branches are mostly bare and its remaining leaves are grey-brown.
Its few olives are discoloured and weather-puckered. “A disaster,”
Mr Arsieni sighs. The olive groves that have encircled Cellino San
Marco since ancient times are now turning into what locals call
tree cemeteries.
The cause is a bacterium called Xylella fastidiosa. Carried by sap-
sucking insects called spittlebugs, it arrived in the port of Gallip-
oli, near the southern tip of Puglia, in 2013. Olive farmers nearby
started to notice that their trees were turning rust-brown. The bac-
teria start in the leaf-tips and work their way into the trunks,
blocking the xylem (the water-carrying arteries) and preventing
the trees from absorbing water. Eventually the trees die. “Xylella
works incredibly fast,” says Eugenio Arsieni, Massimo’s brother.
“If it gets to 10% of the tree, it will soon take over 80%.” The drive to
Cellino San Marco from the nearby port of Brindisi passes fewer
healthy groves than infected ones, their tree crowns bare or
patchy. Last autumn’s olive harvest in Puglia, which supplies al-
most half of Italy’s olive oil, was down 65% on the previous year.
Over 1m olive trees in Italy are thought to have died already, and
this spring the country came perilously close to running out of na-
tive olive oil altogether.
A reminder of the good old days hangs on the wall of the Arsieni
family’s olive-oil shop in the market square of Cellino San Marco.
The aerial photo of the groves in 2017 shows a healthy green sea of
trees. That year production was close to 100% of the normal
amount, explains Eugenio. Last year it was down by 40%. This year
the loss will be more like 70%, he estimates. On a hike around the
family’s land he points to one avenue of skeletal trees: “Last year
these were all green.” Olive oil is the blood of Cellino San Marco. Anolivetree features on the village’s crest, and locals traditionally
test whether they have received the evil eye by putting three drops
of oil into a bowl of water and observing the shape they make. To-
day that world is vanishing. Some farmers are simply abandoning
their land and emigrating; to Australia to restart their farming ca-
reers, or to northern Europe to work in coffee shops. Pugliese olive
presses are being sold off to producers in north Africa.
The speed with which Xylellahas taken hold in Puglia has as-
tonished scientists as much as farmers. Its spread prompted the
euto require Italy to create a buffer zone—with susceptible trees
destroyed and spittlebug-friendly grasses cut—but implementa-
tion has been slow. The bacterium has continued to move north. In
recent months traces have been found in other parts of Italy, such
as Tuscany, and on September 6th France’s Ministry of Agriculture
confirmed that Xylellahad been detected in two olive trees on the
country’s Mediterranean coast. Vytenis Andriukaitis, the Euro-
pean commissioner for health and food safety, calls this “the big-
gest phytosanitary crisis confronting the eufor many years.”Nature versus nurture
Climate change is not the root cause of the Xylella outbreak; it was
probably introduced by an ornamental plant from Costa Rica. But
it appears to explain its drastic spread. In recent years Puglia has
experienced a series of extraordinary weather events, including
uncommonly harsh summer droughts, spring frosts in 2017 and
hailstorms earlier this year. Winters have been cold enough to
weaken the trees, but not cold enough to kill the spittlebug popula-
tions. Riccardo Valentine of the Euro-Mediterranean Centre on
Climate Change has argued that these extreme events have made
the olive trees vulnerable to the bacterium. Climate change also
helps to explain Xylella’s northward spread: Martin Godefroid of
the French National Institute for Agricultural Research and others
have shown that “climate change may strongly impact the distri-
bution” of Xylella, with milder winters making this tropical bacte-
rium viable far north of its natural habitat.
The story in Puglia is not untypical. Climate change is destroy-
ing, or contributing to the destruction of, ancient olive groves
across southern Europe. Unusually hot summers and heavy rains
in Greece have produced surges in the olive-fly populations; the
harvest there is expected to be down 35% this year. In Portugal
droughts have also reduced yields. In Spain, yields are up but water
shortages threaten whole regions in the medium term.
So while the eutreats Puglia as an exception, a place to be quar-
antined, the region typifies wider trends. Centuries-old agricul-
tural firms are going out of business. Nature is being thrown out of
balance. And locals are having to decide whether to fight against
change or to work with it. Elsewhere in Europe that means a choice
between building dykes and giving up land to the sea, or between
continuing to grow hops and switching to vines. In Puglia it means
the choice between anti-Xylellainterventions and adaptation to it.
Examples of the former are plentiful—signs all over Brindisi air-
port warn that taking plants out of the affected zone is “strictly
forbidden”—but ineffective. “You can’t stop Xylella, you can only
live with it,” says Massimo Arsieni. He mourns his family’s ancient
olive trees. But without a cent of help from the euhe has planted 25
hectares (60 acres) of new olive trees of the leccino and favolosa va-
rieties, whose broader arteries are less prone to Xylella’s water-re-
stricting effect. For him, adaptation is the answer. “Look,” he says,
holding out a handful of plump, shiny olives from the new gener-
ation of saplings. “This is the future.” 7Charlemagne Fade to brown
Climate change is destroying ancient olive groves in southern Europe